Whenever we are in Kissimmee/Orlando area we go into Burger King for their whopper sandwiches at $2.19. You just can't beat the price. If you check on the back of your receipt, you can do a survey, and get a free whopper on your next visit, you just have to buy fries and a drink. I also like their side salad as just a buck.
This location is opposite one of our timeshares and it is also great to pop in and get a senior coffee for just 49 cents. The staff are always friendly and this restaurant is fairly quiet.